De-icing agent and method for melting snow and ice

ABSTRACT

The invention relates to a de-icing agent containing a) between 45 and 55 wt. % of an alkali metal acetate, b) between 0.001 and 1 wt. % of a surfactant, c) between 0.0001 and 1 wt. % of an anti-foaming agent, d) between 0.001 and 1 wt. % of a corrosion inhibitor, and a sufficient amount of water to complete 100 wt. %.

The present invention relates to a method of melting snow and/or ice ontraffic areas by applying a deicing composition comprising an aqueoussolution of alkali metal acetate, surfactant, and defoamer, and also tosaid deicing composition.

Snow and/or ice on roads, cycleways, footpaths, bridges, sports grounds,airfields and the like, referred to below as traffic areas, lead to asubstantial impairment in traffic movement and in traffic safety. Forthis reason it has already long been known to apply water-soluble saltsto such areas, the ice and snow melting (thawing) and forming an aqueoussolution of the salt with a correspondingly lowered freezing point, orthe freezing of precipitation, whether in the form of rain or snow orelse simply in the form of freezing fog, being retarded or prevented bythe aqueous solution of alkali metal carboxylates.

If salts are employed as deicing compositions the following requirementsin particular should be met: the salt ought to cause less damage thanexisting thawing compositions, or no damage, let alone destruction, tothe material of which the aforementioned areas are constructed—forexample, concrete to DIN 18500. The salt employed ought to bring aboutrapid and very extensive thawing and/or, in the case of freezingprecipitation, ought to prevent the traffic areas icing up. From theeconomic standpoint, finally, the thawing composition must offer a verygood thawing performance and a long icing prevention time.

In view of the requirements mentioned, deicing compositions specified inthe prior art as being advantageous include primarily alkali metal andalkaline earth metal chlorides and also alkali metal and alkaline earthmetal salts of organic acids. For instance, U.S. Pat. No. 4,855,071 andEP-A-0 579 014 describe alkali metal and/or alkaline earth metalcarboxylates having 1 to 4 carbon atoms, prepared by a particularprocess, as deicing compositions, and especially recommend essentialcalcium/magnesium acetate or sodium acetate.

EP-A-0 483 721 describes a liquid deicing composition composedessentially of water, an alkali metal and/or alkaline earth metalacetate, and specific corrosion inhibitors.

Furthermore, U.S. Pat. No. 5,376,293 also describes mixtures ofdifferent alkali metal and alkaline earth metal carboxylates having acarbon chain length of C₁ to C₃.

The known deicing compositions based on alkali metal chlorides oralkaline earth metal chlorides and based on alkali metal and/or alkalineearth metal carboxylates do not satisfactorily meet the requirementsimposed on a deicing composition.

The action of a salt as a deicing composition is based, as alreadymentioned at the outset, on the lowering of the freezing point of waterby the dissolved cations and anions and on the number of dissolvedparticles per unit volume. Also important, however, for the penetrationrate and the thawing or melting capacity or icing prevention time of athawing composition is the way in which the surface to be deiced iswetted. These factors result not only in an acceleration of the thawingor melting process during the thawing and/or melting of ice and/or snowbut also in a reduction in the amount of thawing composition whenthawing and/or melting ice and/or snow. Moreover, a liquid thawingcomposition better than those already described above ought to becharacterized in that the liquid thawing material is free from solidconstituents and in that it is stable on storage both at temperaturesbelow 0° C. and at temperatures above the freezing point.

It is an object of the invention, accordingly, to develop, out of themultiplicity of deicing compositions in the form of alkali metal and/oralkaline earth metal chlorides and also alkali metal and/or alkalineearth metal carboxylates, a deicing composition which is highlyeffective at lowering the freezing point and which, in connection withthe process of icing up due to freezing precipitation in the form ofsnow, rain or freezing fog or dew, offers a longer freeze protectiontime than comparable thawing compositions. This liquid deicingcomposition ought further to be particularly stable with respect toseparation of the individual components. The deicing composition oughtadditionally, in particular, to be ecologically and physiologicallyunobjectionable, exert little if any corrosive effect on metals and thepaving of traffic areas, and ought to be well tolerated biologically andbe easy to handle and storable. Such a deicing composition would bedesirable in particular in all those cases requiring long-lasting icingprotection and requiring rapid and also prolonged thawing of ice and/orsnow in the surrounding area.

It has surprisingly been found that a specific aqueous solution ofalkali metal acetate in combination with a surfactant and defoamer andwith a suitable corrosion inhibitor in small amounts, in particular anaqueous solution of the potassium salt of acetic acid and a suitablesurfactant and defoamer and corrosion inhibitor in small amounts, hasall of the required properties for application as a deicing composition.

The invention accordingly provides a deicing composition comprising

-   a) from 45 to 55% by weight of an alkali metal acetate,-   b) from 0.001 to 1% by weight of a surfactant,-   c) from 0.0001 to 1% by weight of a defoamer, and-   d) from 0.001 to 1% by weight of a corrosion inhibitor    and also water to 100% by weight.

The invention further provides a method of melting snow and ice ontraffic areas by applying from 5 to 100 g/m² of the deicing compositionof the invention to the traffic area.

The amount of deicing composition to be applied depends in particular onthe external temperature and on the amount of ice and/or snow presentand is preferably from 15 to 80 g/m² of traffic area. The deicingcomposition can be applied using the standard spreading vehicles.

The deicing composition of the invention includes an alkali metalacetate, potassium acetate in particular. The amount of constituent a)is preferably between 47 and 53% by weight, in particular between 48 and52% by weight.

The deicing composition of the invention preferably contains from 0.01to 0.5% by weight, in particular from 0.02 to 0.2% by weight, of one ormore surfactants. Preferred surfactants used are alkyl (poly)glycosides.Their alkyl groups include preferably 8 to 16 carbon atoms.

The deicing composition of the invention contains preferably from 0.0002to 0.1% by weight, in particular from 0.0005 to 0.01% by weight, of oneor more defoamers. Defoamers used are preferably polysiloxanes, inparticular polydialkylsiloxanes, especially polydimethylsiloxanes.

The deicing composition of the invention contains preferably from 0.01to 0.7% by weight of one or more corrosion inhibitors. Corrosioninhibitors used are preferably alkali metal phosphates, alkali metalborates, and alkali metal silicates.

EXAMPLES

The icing prevention time was determined in analogy to ISO 11078 at theparticular air temperature and concrete slab temperature indicated. Inthis case, however, icing was carried out using not electropolishedaluminum sheets but instead concrete slabs measuring 25 cm×25 cm×5 cmwith an inclination angle of 1°. 1.857 g of the specified deicingcomposition were applied to the slabs, corresponding to an applicationrate of 30 g of deicer/m². The measure used for the icing preventiontime is a period of time until the concrete slab starts to ice up. TABLE1 Activity of deicing compositions Icing prevention Temp. Irrigationrate time Example ° C. Deicer g/(dm² · h) min 1 −5 E 5.8 26 2 −5 E 7.419 3 −5 E 8.3 14 4 −15 E 8.1 13 5 −15 E 8.6 14 6 −15 E 9.4 9.5 7 (comp.)−5 potassium formate 5.5 22 8 (comp.) −5 potassium formate 7.6 12 9(comp.) −15 potassium formate 8.4 10 13 (comp.) −15 potassium acetate8.9 7.5E = inventive deicing composition, consisting of a 50% strength byweight aqueous solution of potassium acetate with 0.1% by weight C8 toC₁₆ alkyl glycoside, 0.005% by weight polydimethylsiloxane, and 0.3% byweight K₃PO₄.

For comparison purposes, potassium formate and potassium acetate wereused without additives.

1. A deicing composition comprising: a) from 45 to 55% by weight of an alkali metal acetate, b) from 0.001 to 1% by weight of an alkyl (poly)glycoside, c) from 0.0001 to 1% by weight of a defoamer, d) from 0.001 to 1% by weight of a corrosion inhibitor, and water to 100% by weight.
 2. The deicing composition as claimed in claim 1, wherein the amount of constituent a) is between 47 and 53% by weight.
 3. The deicing composition as claimed in claim 1, wherein the amount of constituent a) is between 48 and 52% by weight.
 4. The deicing composition as claimed in claim 1, wherein constituent a) is potassium acetate.
 5. The deicing composition as claimed in claim 1, wherein the amount of constituent b) is between 0.01 to 0.5% by weight.
 6. The deicing composition as claimed in claim 1, wherein the amount of constituent c) is between 0.0002 to 0.1% by weight.
 7. The deicing composition as claimed in claim 1, wherein constituent c) is a polysiloxane.
 8. The deicing composition as claimed in claim 1, wherein the amount of constituent d) is between 0.01 to 0.7% by weight.
 9. The deicing composition as claimed in claim 1, wherein constituent c) is selected from the group consisting of an alkali metal phosphate, alkali metal borate, alkali metal silicate and mixtures thereof.
 10. A method of melting snow or ice on a traffic comprising the step of applying from 5 to 100 g/m² of the deicing composition as claimed in claim 1 to the traffic area.
 11. A method of melting snow or ice on a surface comprising the step of applying from 5 to 100 g/m² of the deicing composition as claimed in claim 1 to the surface. 